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P7389i – Circuit Description
RF:
Receive
1) The RF Signal from the base station is received through the Antenna
Accessory Connector J600
U150, the switch acts as an isolation between TX and RX. The
provided by U151.This decides whether the Switch is opened for TX or RX and if the
RF is passed to the Aux RF port or the Antenna. This is managed by the following
signals:
TX_EN
RX_EN
H
L
L
H
H
L
L
H
2)
TX_EN
and
RX_EN
respectively.U151
and RF_V1(Q201)
3) Once the received signal is present (using GSM 900 as the example) in the RF switch.
Provided
RX275_GSM_PCS
to the band pass filter FL400, GSM900received frequency will be filtered through,
*Note
RX275_GSM_PCS
FL2400. The DCS 1800 frequency is selected by
through
FL1400
4) For the PCS 1900 and DCS 1800 frequencies the signal is then fed onto the
Select switch U400.
select the appropriate signal; with output tuning being provided by
for DCS and
C2411
5) Once selected the signal will be fed into a Low noise Amplifier Circuit, this part of
the circuit is critical in the achievement of a very low signal to noise ratio, therefore
as can be seen around the actual amplifiers
RX275_GSM
(Q110)) and
(Q2102)), a large amount of external frequency matching and noise reduction
circuitry is involved.
6) The appropriate signal is then fed onto
(For GSM 900) where any existing harmonics or other unwanted frequencies are
removed.
Motorola Internal Use
and is fed to Pin 10 or Pin 3 respectively of the
SW_RF (50Ω Load)
Loaded
Loaded
Not Loaded
Not Loaded
are produced by
Whitecap U800,
is supported by the voltages
(Q2101) is high, then the received signal will be passed
also selects the PCS 1900 frequency passed through
The signal
RVCO_PCS
for PCS.
Q1400
for DCS / PCS (supported by
FL1401
RF Switch control
TX through J600
RX through J600
TX through Antenna
RX through Antenna
Pins C1 and E3
FILTERED
–5V(From
RX275_DCS
and
RVCO_DCS
Q400
for GSM (supported by
(For GSM 1800 / 1900) or
2
A1
or from the
RF Switch
is
Result
–5V
(U903))
(Q110) and passed
DCS/PCS
(Q1100) will then
L1411
and
C1411
RX275_DPCS
FL401
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